Another electrical gremlin thread

my turn to ask for help.

Short TLDR version: Power locks have gone total apesh*t. Never was a problem until.. our first cold spell. ‘Cold’ being about 45*F outside.


Here’s what we KNOW:

-Tahoe PPV with dual battery set up.
-Truck comes from rust belt and as such:
-Both the chassis ground on passenger side frame rail and grounds on driver side frame rail were quite rusty and corroded. Cleaned these grounds thoroughly with wire brush (more on that in a sec)
-Cleaned all battery contacts, terminals, and the terminals at the battery isolator relay
-Secondary battery has a date of 12/21..making it exactly 3 years old. It is also a cheapo no name brand battery.. so I’m thinking “problem”
-No date on primary battery. It is AC/Delco

Using a digital multimeter:
-Primary battery is reading 12.66v (one hour sitting)
-Secondary battery is reading 12.54v (one hour sitting)
-Charging system is reading between 14.4 and 14.5 between both batteries

BACKSTORY:

Last week we had our first “cold” of the year. About 45*F. After a short drive up the street I parked the truck and as I was getting out swore I heard the power locks activate, but wasn’t entirely sure and the door was unlocked because I had just opened it.. I pressed the door lock button on the door and went inside.

Next morning, it’s a bit warmer out. Around 55*F and sunny. go to get in truck and it is unlocked. Thought it was weird but didn’t think too much of it again.. maybe I pressed the door unlock button while coming out on key fob and didn’t realize it. Go to get breakfast, door locks start freaking out. Unlocking itself every 30 seconds or so.. keep it mind that it is only the driver door lock unlocking itself, not any of the others.

I’m actually off this day so I decide go drive around for awhile, truck stays locked, no issues. Then it begins acting temperamental. Unlocking itself in various increments of time, anywhere from 10 seconds to 15 minutes or more without issue before again unlocking itself. Watching the dummy gauge on the dash, it’s reading below 14, roughly 12V. Some time later, Dummy gauge eventually goes up to over 14V. Problem persists.

It is getting considerably worse. Dummy gauges read 14v. Now I cannot lock the vehicle at all without it unlocking itself within 5 minutes. To some people, this is just an annoying gremlin. To me though it is a much bigger deal. I live in very high traffic, NOT very good area, with a lot of creeps and weirdos regularly passing by on foot and car. Even worse, just a couple of months ago our household was a victim of auto theft when they stole my wife’s car right out of our driveway. Not being able to lock the truck is a major security issue and it’s pissing me off BIG time….

Pics of GROUNDS:

Before


After


Before


After


And a little more info on those grounds… The chassis ground on the passenger side frame rail was actually somewhat loose when I took it off !!! Not super loose but it was NOT tight as it should have been. When I went to reinstall the bolt after cleaning, it just threaded indefinitely but would not tighten. Not even a little. Great. I went into my stash of extra bolts and pulled out one that was similar. It did tighten but not as much as I wanted, it too, just spins freely. I got it basically to stay at “hand tight”.. being where our roads might as well be gravel highways I’m definitely worried about it coming aloose. How big of an issue is this ?

Was thinking the secondary battery is bad but would it really cause this kind of issue? I’ve had many a batteries go weak and/or die on me over the years and never experienced anything like this. Also I’d be gutted if I went and spend $200 on a battery for the freakin door to start unlocking itself again once I put the terminals back on…

So, battery bad? Alternator bad? something else?


I would be most gracious for any advice.

Whats TLDR?

Kidding above….

Actually sounds like your loose-ish ground is the problem and make sure your door switches are working, as in the latch on the door that go to the b and c pillars…
I would take a screwdriver and ‘close the latch’ with all the doors open and lock them then play with the latches a little especially the drivers door.

My driver's side ground threads on the body mount were stripped so I used a bolt and nut there, with the head toward the tire. I didn't want to subject the bolt end threads to what the tire tosses up.

As stated above, you need to make that ground connection tight. Many unusual things happen with these trucks when the grounds are not clean and tight. Also, when batteries or battery cables (typically rot from the inside out) are not in good shape, unusual things happen as well.

I recommend that you get both batteries load tested on a bench at a local auto parts store to ensure that they are delivering adequate amperes as well as voltage.

OK fellas, I appreciate the responses thus far.

I will:

-Find a way to fix the passenger side ground (see below)
-Play with the door latches themselves and observe their behavior*
-Remove the batteries and have them bench tested


But in the meantime I have a small update that is relevant:

Warm front came through last night. At the breakadawn it was 65*F and sunny. Go to get in the truck a little later(9AM) and… it’s still locked from last night. I wanted to put the multimeter on the batteries to test after a night of sitting but I was sort of in a rush. Drove around all morning and it (the ambient temperature) continued to warm up. 2 1/2 hours of the engine running continuously between driving and sitting in the truck idling. At this point it is exactly 70*F and sunny with light breeze- aka what is known as a “perfect day”. Door locks didn’t freak out not once. Continue through the day, I drove around for another hour and a half taking care of stuff. Drive around… Park truck... Get out... Lock doors… Come back… Doors still locked.. rinse, repeat. It should be known that the dummy gauges read about 12v on the dash even after running continuously for over 2 hours. Eventually , dummy gauge got up to 14v.

This is the warmest day we’ve had since this issue started as I noted in the OP. To me this points directly to an issue related to the cold which really leads to one general thing: the batteries or the charging system.

However, this issue is far from solved *and* I am NOT ruling out an issue with the ground not being tight enough as you guys have alluded to. So, any suggestions on how to take care of that? The problem with the passenger side chassis ground is that the factory mounting position does not allow for access from the rear unlike the driver side grounds.

I am thinking about relocating the aforementioned ground by drilling a new hole somewhere close by, where I could have access to both sides and stick a locking nut or something on it to make sure it stays real tight… good idea? Obviously it won’t be able to be too far as I don’t want the ground strap itself to have too much tension.. What would you guys do ?

*as for the door latches, what exactly am I looking for to say they (driver’s door latch particularly) are not functioning properly .. too much/not enough play compared to the other latches?

PPV_2018 said:

OK fellas, I appreciate the responses thus far.

I will:

-Find a way to fix the passenger side ground (see below)
-Play with the door latches themselves and observe their behavior*
-Remove the batteries and have them bench tested


But in the meantime I have a small update that is relevant:

Warm front came through last night. At the breakadawn it was 65*F and sunny. Go to get in the truck a little later(9AM) and… it’s still locked from last night. I wanted to put the multimeter on the batteries to test after a night of sitting but I was sort of in a rush. Drove around all morning and it (the ambient temperature) continued to warm up. 2 1/2 hours of the engine running continuously between driving and sitting in the truck idling. At this point it is exactly 70*F and sunny with light breeze- aka what is known as a “perfect day”. Door locks didn’t freak out not once. Continue through the day, I drove around for another hour and a half taking care of stuff. Drive around… Park truck... Get out... Lock doors… Come back… Doors still locked.. rinse, repeat. It should be known that the dummy gauges read about 12v on the dash even after running continuously for over 2 hours. Eventually , dummy gauge got up to 14v.

This is the warmest day we’ve had since this issue started as I noted in the OP. To me this points directly to an issue related to the cold which really leads to one general thing: the batteries or the charging system.

However, this issue is far from solved *and* I am NOT ruling out an issue with the ground not being tight enough as you guys have alluded to. So, any suggestions on how to take care of that? The problem with the passenger side chassis ground is that the factory mounting position does not allow for access from the rear unlike the driver side grounds.

I am thinking about relocating the aforementioned ground by drilling a new hole somewhere close by, where I could have access to both sides and stick a locking nut or something on it to make sure it stays real tight… good idea? Obviously it won’t be able to be too far as I don’t want the ground strap itself to have too much tension.. What would you guys do ?

*as for the door latches, what exactly am I looking for to say they (driver’s door latch particularly) are not functioning properly .. too much/not enough play compared to the other latches?

Click to expand...

The latches now hold the switch for the interior lights, door locks etc instead of the little push button that used to be in the jamb. So if its not completely hitting the switch or its loose my thoughts were that maybe as you drive and it sees the door as not fully closed so its unlocking locking the doors but then again now that i think about it when you put it in drive and get up to speed 5- 10-15-20 mph do your doors lock? Do they unlock when you put it in park? Do you have a dic switch on the steering wheel or dash? If you do there are options to turn that stuff on or off …. Or maybe you shift lever is loose? This all comes back to bcm and grounds i bet… just thinking outloud …

Sorry, I’ve been sidelined for a couple days. Haven’t even driven the truck since my last post until today.

PG01 said:

now that i think about it when you put it in drive and get up to speed 5- 10-15-20 mph do your doors lock? Do they unlock when you put it in park? Do you have a dic switch on the steering wheel or dash? If you do there are options to turn that stuff on or off …. Or maybe you shift lever is loose? This all comes back to bcm and grounds i bet… just thinking outloud …

Click to expand...

So in response to this, the door locks otherwise function normally. When I put the truck in drive, all the doors lock. When I put the truck in park, all the doors unlock (at least the driver and passenger door, never paid too much attention to back doors). Shift lever seems fine. This problem is totally isolated to the driver’s door unlocking on it’s own.

So like i say I’ve been sidelined for a few days so i haven’t been able to play around with it… but here’s a small update none-the-less

Today has been the warmest since I’ve started this thread. 79*F outside. Come out to the truck in the morning, all the doors are still locked! Apparently they’ve been locked since I parked the truck a few days ago. Just for fun i stuck the meter on the batteries to check them since the truck has been sitting a while

Secondary battery : 12.41v
Primary battery: 12.71v

Need to take a ~60 mile trip, so I jump in the truck and take off. Wouldn’t you know the door lock is going mad. For the first 10 miles it’s just going crazy unlocking itself at various increments.. because of the temperature being so much warmer than before, I’m now convinced it is NOT weak battery related.

I did notice, that going over bumps/potholes/connecting infrastructure (ie: bridge to pavement) that were hard enough to rattle the truck seemed to trigger a couple of intermittent “unlocks”.. coincidence? At this point I am thinking “not”. This has me ready to lock in (no pun intended) on that suspect ground. It is beginning to seem probable that sus ground is the culprit here as you guys have suggested.

Furthermore, once I made it to my destination, I had several places that I parked, and locked the truck. First location the truck had unlocked itself when I came back to it. But all the other stops the truck had actually stayed locked while I was away from it!! The whole entire ride home (~60+ miles), the locks did not freak out once.

Sounding more and more like the ground wouldn’t you guys say? I know I really need to get to the root of this, but just have not been able to address it yet. I will update this thread again once I am able to relocate the chassis ground underneath the truck.

I'd recommend a voltage drop test for both the positive and negative circuits between the battery, engine, and body. That will tell you if the main grounds can handle the loads.

Yesterday i took both batteries out of the truck to go get tested. Bring them in the store, guy hooks them up, says he’s having problems with his tester. Gets the aux battery to give a reading and he says that it’s good. Eventually he takes both of batteries to the back and hooks them up to the charger in order to get proper readings. Comes back and tells me both batteries are in great shape ! He says he was surprised the aux battery was so strong given the date of 12/21 on it. Seemed like an honest young dude but I was still surprised he didn’t try to upsell. He did recommend getting an AGM or deep cycle battery for the aux when it did finally give out, but that for today all was well.




So, come back home to start messing with the ground again. Searching for a suitable new location i saw that there was a pre drilled hole close to the body mount. I’m thinking to myself, this is going to be too easy.

the hole was only sliiiiiiightly too small, so i used a drill bit to just open it up a bit. wire brush it up, Stick the eyelet and bolt through, put a nut on the bottom, tighten, put the batteries back in, done.

Get in the truck for a test run .. within 2 minutes, locks freaking out. Feeling defeated i come back, and start analyzing the new ground location.


Turns out that 1.) it doesn’t look like I did a great job prepping the surface area as there was still dirt and what looked to be paint, so not contact with bare metal, and 2.), the “new” mounting location was very close to a lip/ basically a weld right under the body mount, so close that it seems like the washer was making contact and not sitting completely flush .. d’oh !!


(The “new” ground location not suitable because it’s not flush. Also factory mounting hole visible at the top)

So, start drilling a new hole from scratch close by and realize that I’m in the wrong spot because I’m still close to that little welded lip. Mark the projected new spot with a paint pen and drill through. once again, use a new wire brush to clean the area and mount the eyelet and bolt. This time it’s sitting flush and super, super tight.



(Final “new” ground location, top view)



(Final “new ground location, bottom view)


So…

After that, drove around yesterday and today, NO door lock craziness. I was so ready to slap *SOLVED* on the title of this thread and be done with it all ..

Until an hour ago. Went to run a quick errand and i hear the dreaded sound of the door unlocking.

For the hell of it, I said I will just go right ahead and have the battery in the key fob replaced since there is a place that does it right in my neighborhood. Cheap troubleshooting and even if it doesn’t work at least i have a new battery in the fob. Dude puts a new battery in the fob and I’m on my way.

Come back up to the truck, and it unlocks itself as I’m standing outside (it had already done it while I wasn’t close anyways because I could see the door lock sticking up as I approached).. So I try locking the truck with the fob as I stand outside and it *INSTANTANEOUSLY* unlocks itself. Try again. Same result. Tried like 5 more times (definition of insanity) and it instantly unlocks itself each time. JFC!!

While I was under the hood yesterday, I did peel back as much insulation as possible to check for corrosion as you guys have suggested. All I saw was crispy clean looking copper every time.

So far:

- the battery cables *look* good from what i can tell
- grounds on driver and passenger frame rails are clean and SUPER tight
- autozone says both batteries are in great shape
- new key fob battery

And still, door lock insanity persists..

This is some bs.

Fless said:

I'd recommend a voltage drop test for both the positive and negative circuits between the battery, engine, and body. That will tell you if the main grounds can handle the loads.

Click to expand...

Just being honest, I’m not really sure how to perform that test or what exactly that i would be looking for



Edit: you know, i forgot about the door latch thing too. I will go check those out in a little while.

Double edit: door lock mechanisms seem fine.. no excessive play, they seem to just operate normally. Plus no DIC message about doors being open.